Diet of moulting Swainson's Thrushes (Catharus ustulatus) and Tennessee Warblers (Leiothlypis peregrina) at a stopover site during fall migration measured with fecal DNA metabarcoding.

Moult and migration are energetically demanding and require adequate nutrition. In some species, individuals may interrupt their fall migration to moult at discrete stopover locations outside of their breeding grounds (i.e., moult-migration) leading to competing nutritional demands for moult and migration. Here, we use DNA barcoding of fecal samples to compare the diet of moulting and actively migrating (post-moult) Swainson's Thrushes (Catharus ustulatus) and Tennessee Warblers (Leiothlypis peregrina) during their fall migration stopover at a large urban greenspace in Montreal, Canada. Diet differed according to moult status, species, and seasonality. Swainson's Thrushes had a broad diet with frequent detections of both insects and berry-producing shrubs; while detections in Tennessee Warblers' diets were mainly arthropods. For both species, more actively migrating individuals consumed fleshy-fruiting plants than moulting individuals. A higher proportion of moulting birds consumed arthropods compared to active migrants, due to either arthropod availability or a dietary preference for proteinaceous foods to grow feathers. Both species and moult classes consumed more native plants than non-native plants later in the season. We show the importance of managing urban greenspaces with native plants and diverse food sources that can provide for the different dietary needs of migratory birds.

Community-science reveals delayed fall migration of waterfowl and spatiotemporal effects of a changing climate.

Climate change has well-documented, yet variable, influences on the annual movements of migratory birds. The effects of climate change on fall migration remains understudied compared with spring but appears to be less consistent among species, regions and years. Changes in the pattern and timing of waterfowl migration in particular may result in cascading effects on ecosystem function, and socio-economic and cultural outcomes. We investigated changes in the migration of 15 waterfowl species along a major flyway corridor of continental importance in northeastern North America using 43 years of community-science data. We built spatially- and temporally explicit hierarchical generative additive models for each species and demonstrated that climate, specifically the interaction between minimum temperature and precipitation, significantly influences migration phenology for most species. Certain species' migratory movements responded to specific temperature thresholds (climate migrants) and others reacted more to the interaction of temperature and precipitation (extreme event migrants). There are already significant changes in the fall migration phenology of common waterfowl species with high ecological and economic importance, which may simply increase in the context of a changing climate. If not addressed, climate change could induce mismatches in management, regulations and population surveys which would negatively impact the hunting industry. Our findings highlight the importance of considering species-specific spatiotemporal scales of effect on climate on migration and our methods can be widely adapted to quantify and forecast climate-driven changes in wildlife migration.

Les changements climatiques ont des influences bien documentées, mais variables, sur les mouvements annuels des oiseaux migrateurs. Les effets des changements climatiques sur les migrations automnales demeurent peu étudiés par rapport aux migrations printanières, mais il semble qu'ils soient moins constants d'une espèce, d'une région et d'une année à l'autre. Les changements dans le patron et le calendrier de la migration de la sauvagine en particulier peuvent avoir des effets en chaîne sur la fonction des écosystèmes et des impacts socio­économiques et culturels. Nous avons étudié les changements dans la migration de 15 espèces de sauvagine le long d'un corridor de migration d'importance continentale dans le nord­est de l'Amérique du Nord, en utilisant 43 ans de données scientifiques communautaires. Nous avons construit des modèles additifs généralisés hiérarchiques spatialement et temporellement explicites pour chaque espèce et avons démontré que le climat, en particulier l'interaction entre la température minimale et les précipitations, influence de manière significative la phénologie de la migration pour la plupart des espèces. Les mouvements migratoires de certaines espèces répondent à des seuils de température spécifiques (migrateurs climatiques) et d'autres réagissent davantage à l'interaction entre la température et les précipitations (migrateurs d'événements extrêmes). La phénologie des migrations automnales d'espèces de sauvagine commune qui ont une grande importance écologique et économique connaît déjà des changements importants, qui pourraient simplement s'accentuer dans le cadre des changements climatiques. S'ils ne sont pas pris en compte, les changements climatiques pourraient induire des décalages dans la gestion, les réglementations et les enquêtes de population, ce qui aurait un impact négatif sur l'industrie de la chasse. Nos résultats soulignent l'importance de prendre en compte les échelles spatio­temporelles spécifiques sur la migration et nos méthodes peuvent être largement adaptées pour quantifier et prévoir les changements induits par le climat dans la migration de la faune.

Central-place foraging poses variable constraints year-round in a neotropical migrant.

BACKGROUND: "Central-place foragers" are constrained in their habitat selection and foraging range by the frequency with which they need to return to a central place. For example, chick-rearing songbirds that must feed their offspring hourly might be expected to have smaller foraging ranges compared to non-breeding songbirds that return nightly to a roost. METHODS: We used GPS units to compare the foraging behaviour of an aerial insectivorous bird, the purple martin (Progne subis), during the breeding season in three regions across North America, as well as the non-breeding season in South America. Specifically, we tested foraging range size and habitat selection. RESULTS: Foraging range did not vary among regions during breeding (14.0 ± 39.2 km2) and was larger during the nonbreeding period (8840 ± 8150 km2). Purple martins strongly preferred aquatic habitats to other available habitats year-round and in the Amazon commuted from night roosts in low productivity sediment-poor water, where risk of predation was probably low, to daytime foraging sites in productive sediment-rich water sites. CONCLUSIONS: We provide the first estimates for foraging range size in purple martins and demonstrate foraging preference for aquatic habitats throughout two stages of the annual cycle. Understanding foraging constraints and habitat of aerial insectivores may help plan conservation actions throughout their annual cycle. Future research should quantify foraging behaviour during the post-breeding period and during migration.

Spatial structure in migration routes maintained despite regional convergence among eastern populations of Swainson's Thrushes.

BACKGROUND: Migratory connectivity links the different populations across the full cycle and across the species range and may lead to differences in survival among populations. Studies on spatial and temporal migratory connectivity along migration routes are rare, especially for small migratory animals. METHODS: We used an automated radio-telemetry array to assess migratory connectivity en route and between early and later stages of the fall migration of the eastern populations of Swainson's Thrush, and to assess the variation of migration pace between consecutive detection from the different receiving stations along the migratory journey. We tracked 241 individuals from across eastern Canada to determine if populations were mixing around the Gulf of Mexico. We also tested the influence of tagging longitude, latitude and age on migration pace. RESULTS: Migration routes varied and converged towards the northeast coast of the Gulf of Mexico, but in this region, populations maintained finer-scale spatial structure. Migration pace increased as birds progressed south, independent of age and tagging site. CONCLUSIONS: We showed that for songbirds, migratory connectivity can be maintained at fine spatial scales despite the regional convergence of populations, highlighting the importance of detailed spatial tracking for identification of population specific migration routes. Overall, our study provides a portrait of migratory movements of eastern Swainson's Thrush and a framework for understanding spatial structure in migration routes for other species.

Point-of-care blood analyzers measure the nutritional state of eighteen free-living bird species.

Point-of-care devices offer the potential to democratize a suite of physiological endpoints and assess the nutritional state of wild animals through plasma metabolite profiling. Measurements of plasma metabolites typically occur on frozen tissue in the laboratory, thus dissociating measurements from field observations. Point-of-care devices, widely used in veterinary and human medicine, provide rapid results (seconds or minutes) allowing in situ measurements of wild animals in remote areas without the need for access to freezers. Using point-of-care devices, we measured glucose, triglyceride, cholesterol and ß-hydroxybutyrate levels in plasma from 18 wild bird species spanning nine families and three orders. The values from six different point-of-care devices correlated strongly with one another, and with traditional laboratory measurements from stored plasma (R2 = 0.70-0.90). Although POC devices provided accurate relative values in wild birds, absolute values varied from laboratory measurements by up to 50% illustrating the need for calibration equations. Furthermore, three case studies showed the potential for point-of-care devices at research stations where participants do not have access to a lab and sample preservation is difficult: (i) at a remote seabird colony, birds that were provided with supplemental food had higher levels of glucose and lower ß-hydroxybutyrate and cholesterol levels than unfed birds, suggesting they were in a better nutritional state; (ii) at a migration monitoring station, levels of triglycerides of two migratory songbirds increased with time of day, implying that they were fattening during stopover; and (iii) for diving seabirds, individuals that worked harder (shorter surface intervals) had higher glucose and lower ß-hydroxybutyrate implying that nutritional state is an index of foraging effort and success. We demonstrate that point-of-care devices, once validated, can provide accurate measurements of the nutritional state of wild birds. Such real-time measurements can aid in ecological research and monitoring, care of wildlife at rehabilitation centres, and in veterinary medicine of exotics.